1. Field of the Invention
The present invention relates to a ultraviolet ray absorbent glass in which a ultraviolet ray absorbent film is formed on a glass surface.
2. Discussion of Background
It is important to interrupt ultraviolet rays entering into rooms or the cabin of automobiles from the viewpoint of not only preventing sunburn to human bodies but also preventing the deterioration of ornaments in the rooms or the cabin of automobiles.
Heretofore, there have been known to use organic compounds such as benzophenone, benzotriazole and so on as absorbing agents. However, such organic compounds have a disadvantage that they are easily deteriorated with the absorption of ultraviolet rays. In view of the disadvantage, several methods have been proposed wherein an inorganic compound such as zinc oxide, titanium oxide, cerium oxide or the like which does not cause deterioration and has a ultraviolet ray absorbing function is used and a film of the inorganic compound is formed on the surface of a substrate glass to thereby form a ultraviolet ray absorbent glass.
However, the above-mentioned method had a disadvantage as follows. When the oxide is used to form a film on an ordinary glass plate, iridescence was apt to occur in the reflection light due to interference of light because there was a large difference between the refractive indices of the substrate glass and the film of the oxide.
In particular, when a thin film (less than 100 nm) is formed on the substrate glass to impart a ultraviolet ray absorbing function, the ultraviolet absorptive power is insufficient although it can minimize the iridescence in the reflection light due to interference of light. On the other hand, a thick film (more than 800 nm) is formed, it has problems in the strength of the films, the transmittance of visible light and productivity although it can eliminate interference color. Accordingly, in many cases, films having a film thickness range which may cause interference color, are formed. Therefore, the problem of iridescence is unavoidable in a case that a ultraviolet ray absorbent glass is manufactured by using these oxides.
Further, in a summer season, heat of sunlight increases temperature in rooms to reduce cooling efficiency. In order to prevent the disadvantages, there has been an important problem to limit the entering of the sunlight into the rooms to improve the cooling efficiency by imparting heat ray reflectivity to glass plates for automobiles, buildings and so on.
Recently, heat ray reflecting glass which is obtained by forming on a glass surface a film formed of material such as a noble metal, a metallic oxide having electric conductivity or a nitride is mainly used. However, such film is insufficient to absorb ultraviolet rays. Further, it absorbs much visible light depending on material used. Accordingly, the heat ray reflecting glass can not be used as glass required to have a high visible light transmittance, for automobiles, buildings and so on.
Further, there has been proposed a technique of forming a transparent ornament on or in a glass plate by coating a material having a refractive index different from the above-mentioned glass plate, whereby a design is added to the glass plate (Japanese Unexamined Patent Publication No. 247539/1991).
Since metallic oxides such as zinc oxide, titanium oxide, cerium oxide or the like which is used for the film for absorbing ultraviolet rays have a higher refractive index than glass, they can be used for a film for forming the transparent ornament. However, the glass plate having the transparent ornament has a portion which does not partially interrupt ultraviolet rays.